maemo.org - Talk - Accessing Bluetooth LE devices

I recently got a HRM belt thingy (made by MagellanGPS) that I'd like to integrate to my system. The belt uses Bluetooth LE to communicate with a host controller so the first thing to do is to create a BTLE controller for it.

I found an article by @javispedro that describes how it can be done, and as I already have nodejs on my device I decided to use the "noble" npm to implement it.

My first rough idea is to have a small nodejs servlet script that connects to the HRM device and presents the gathered heartbeat data in a local socket. This way it is really easy to write a QML client for presentation or integrate it to a sportstracking application.

Prerequisities:

basic set of development utils, but of course everybody has these already: make, gcc, gcc-c++, rpmbuild, etc...
a somewhat recent nodejs version. I have v0.12.7 but probably anything newer than 0.10.something is OK
pkcon install bluez-libs-devel systemd-devel
npm install noble

That's all it takes really. You'll find some nice exmples under node_modules/noble/examples that give overview of the service discovery and use.

However, it seems that even though I can scan for devices and find the HRM belt, I cannot connect to it:

Code:

[root@Jolla examples]# 

[root@Jolla examples]# node advertisement-discovery.js 

peripheral discovered (eca6b680cd95 with address <ec:a6:b6:80:cd:95, random>, connectable true, RSSI -70:

        hello my local name is:

                HRM (Ver0.4)

        can I interest you in any of the following advertised services:

                ["180d"]

The belt seemingly offers a service 180d which most probably is the heartbeat monitoring, but it stays in disconnected mode:

Code:

{ _noble: 

   { state: 'poweredOn',

     _bindings: 

      { _state: 'poweredOn',

        _addresses: [Object],

        _addresseTypes: [Object],

        _connectable: [Object],

        _pendingConnection: false,

        _connectionQueue: [],

        _handles: {},

        _gatts: {},

        _aclStreams: {},

        _hci: [Object],

        _gap: [Object],

        _events: [Object],

        onSigIntBinded: [Function],

        _scanServiceUuids: [] },

     _peripherals: { eca6b680cd95: [Circular] },

     _services: { eca6b680cd95: {} },

     _characteristics: { eca6b680cd95: {} },

     _descriptors: { eca6b680cd95: {} },

     _discoveredPeripheralUUids: [ 'eca6b680cd95' ],

     _events: 

      { warning: [Function],

        stateChange: [Function],

        discover: [Function] },

     _allowDuplicates: undefined },

  id: 'eca6b680cd95',

  uuid: 'eca6b680cd95',

  address: 'ec:a6:b6:80:cd:95',

  addressType: 'random',

  connectable: true,

  advertisement: 

   { localName: 'HRM (Ver0.4)',

     txPowerLevel: undefined,

     manufacturerData: undefined,

     serviceData: [],

     serviceUuids: [ '180d' ] },

  rssi: -70,

  services: null,

  state: 'disconnected' }

Does anybody have better experience on BTLE, aome advice on how the connection should be attempted?